package local.media;

/**
 * G.711 codec. This class provides methods for u-law, A-law and linear PCM
 * conversions.
 */
public class G711 {
	static final int SIGN_BIT = 0x80; // Sign bit for a A-law byte.
	static final int QUANT_MASK = 0xf; // Quantization field mask.
	static final int NSEGS = 8; // Number of A-law segments.
	static final int SEG_SHIFT = 4; // Left shift for segment number.
	static final int SEG_MASK = 0x70; // Segment field mask.

	static final int[] seg_end = { 0xFF, 0x1FF, 0x3FF, 0x7FF, 0xFFF, 0x1FFF, 0x3FFF, 0x7FFF };

	// copy from CCITT G.711 specifications

	/** u- to A-law conversions */
	static final int[] _u2a = { 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,
			19, 20, 21, 22, 23, 24, 25, 27, 29, 31, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 46, 48, 49, 50, 51,
			52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79,
			81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105,
			106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126,
			127, 128 };

	/** A- to u-law conversions */
	static final int[] _a2u = { 1, 3, 5, 7, 9, 11, 13, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30,
			31, 32, 32, 33, 33, 34, 34, 35, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 48, 49, 49, 50, 51,
			52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77,
			78, 79, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102,
			103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123,
			124, 125, 126, 127 };

	static int search(int val, int[] table) {
		for (int i = 0; i < table.length; i++)
			if (val <= table[i])
				return i;
		return table.length;
	}

	/**
	 * Converts a 16-bit linear PCM value to 8-bit A-law.
	 *
	 * It accepts an 16-bit integer and encodes it as A-law data.
	 *
	 * Linear Input Code Compressed Code ----------------- ---------------
	 * 0000000wxyza 000wxyz 0000001wxyza 001wxyz 000001wxyzab 010wxyz 00001wxyzabc
	 * 011wxyz 0001wxyzabcd 100wxyz 001wxyzabcde 101wxyz 01wxyzabcdef 110wxyz
	 * 1wxyzabcdefg 111wxyz
	 *
	 * For further information see John C. Bellamy's Digital Telephony, 1982, John
	 * Wiley & Sons, pps 98-111 and 472-476.
	 */
	public static int linear2alaw(int pcm_val) // 2's complement (16-bit range)
	{
		int mask;
		int seg;
		// unsigned char aval;
		int aval;

		if (pcm_val >= 0) {
			mask = 0xD5; // sign (7th) bit = 1
		} else {
			mask = 0x55; // sign bit = 0
			pcm_val = -pcm_val - 8;
		}

		// Convert the scaled magnitude to segment number.
		seg = search(pcm_val, seg_end);

		// Combine the sign, segment, and quantization bits.
		if (seg >= 8) // out of range, return maximum value.
			return (0x7F ^ mask);
		else {
			aval = seg << SEG_SHIFT;
			if (seg < 2)
				aval |= (pcm_val >> 4) & QUANT_MASK;
			else
				aval |= (pcm_val >> (seg + 3)) & QUANT_MASK;
			return (aval ^ mask);
		}
	}

	/**
	 * Converts an A-law value to 16-bit linear PCM
	 */
	// public static int alaw2linear(unsigned char a_val)
	public static int alaw2linear(int a_val) {
		int t;
		int seg;
		a_val ^= 0x55;
		t = (a_val & QUANT_MASK) << 4;
		// seg=((unsigned)a_val&SEG_MASK)>>SEG_SHIFT;
		seg = (a_val & SEG_MASK) >> SEG_SHIFT;
		switch (seg) {
			case 0:
				t += 8;
				break;
			case 1:
				t += 0x108;
				break;
			default:
				t += 0x108;
				t <<= seg - 1;
		}
		return ((a_val & SIGN_BIT) != 0) ? t : -t;
	}

	/** Bias for linear code. */
	public static final int BIAS = 0x84;

	/**
	 * Converts a linear PCM value to u-law
	 *
	 * In order to simplify the encoding process, the original linear magnitude is
	 * biased by adding 33 which shifts the encoding range from (0 - 8158) to (33 -
	 * 8191). The result can be seen in the following encoding table:
	 *
	 * Biased Linear Input Code Compressed Code ------------------------
	 * --------------- 00000001wxyza 000wxyz 0000001wxyzab 001wxyz 000001wxyzabc
	 * 010wxyz 00001wxyzabcd 011wxyz 0001wxyzabcde 100wxyz 001wxyzabcdef 101wxyz
	 * 01wxyzabcdefg 110wxyz 1wxyzabcdefgh 111wxyz
	 *
	 * Each biased linear code has a leading 1 which identifies the segment number.
	 * The value of the segment number is equal to 7 minus the number of leading
	 * 0's. The quantization interval is directly available as the four bits wxyz.
	 * The trailing bits (a - h) are ignored.
	 *
	 * Ordinarily the complement of the resulting code word is used for
	 * transmission, and so the code word is complemented before it is returned.
	 *
	 * For further information see John C. Bellamy's Digital Telephony, 1982, John
	 * Wiley & Sons, pps 98-111 and 472-476.
	 */
	public static int linear2ulaw(int pcm_val) // 2's complement (16-bit range)
	{
		int mask;
		int seg;
		// unsigned char uval;
		int uval;

		// Get the sign and the magnitude of the value.
		if (pcm_val < 0) {
			pcm_val = BIAS - pcm_val;
			mask = 0x7F;
		} else {
			pcm_val += BIAS;
			mask = 0xFF;
		}
		// Convert the scaled magnitude to segment number.
		seg = search(pcm_val, seg_end);

		// Combine the sign, segment, quantization bits; and complement the code word.

		if (seg >= 8)
			return (0x7F ^ mask); // out of range, return maximum value.
		else {
			uval = (seg << 4) | ((pcm_val >> (seg + 3)) & 0xF);
			return (uval ^ mask);
		}
	}

	/**
	 * ConvertS a u-law value to 16-bit linear PCM.
	 *
	 * First, a biased linear code is derived from the code word. An unbiased output
	 * can then be obtained by subtracting 33 from the biased code.
	 *
	 * Note that this function expects to be passed the complement of the original
	 * code word. This is in keeping with ISDN conventions.
	 */
	// public static int ulaw2linear(unsigned char u_val)
	public static int ulaw2linear(int u_val) {
		int t;
		// Complement to obtain normal u-law value.
		u_val = ~u_val;
		// Extract and bias the quantization bits. Then shift up by the segment number
		// and subtract out the bias.
		t = ((u_val & QUANT_MASK) << 3) + BIAS;
		// t<<=((unsigned)u_val&SEG_MASK)>>SEG_SHIFT;
		t <<= (u_val & SEG_MASK) >> SEG_SHIFT;

		return ((u_val & SIGN_BIT) != 0) ? (BIAS - t) : (t - BIAS);
	}

	/**
	 * A-law to u-law conversion.
	 */
	// public static int alaw2ulaw(unsigned char aval)
	public static int alaw2ulaw(int aval) {
		aval &= 0xff;
		return ((aval & 0x80) != 0) ? (0xFF ^ _a2u[aval ^ 0xD5]) : (0x7F ^ _a2u[aval ^ 0x55]);
	}

	/**
	 * u-law to A-law conversion.
	 */
	// public static int ulaw2alaw(unsigned char uval)
	public static int ulaw2alaw(int uval) {
		uval &= 0xff;
		return ((uval & 0x80) != 0) ? (0xD5 ^ (_u2a[0xFF ^ uval] - 1)) : (0x55 ^ (_u2a[0x7F ^ uval] - 1));
	}

	/** PCM ecoder/decoder tests. */
	/*
	 * public static void main(String[] args) { for (int i=0; i<0xFF; i++) { int
	 * pcmu,pcma,linear; pcmu=i; System.out.print("  pcmu:"+pcmu);
	 * pcma=ulaw2alaw(pcmu); System.out.print("  pcma:"+pcma); pcmu=alaw2ulaw(pcma);
	 * System.out.print("  pcmu:"+pcmu); linear=alaw2linear(pcma);
	 * System.out.print("  linear:"+linear); pcma=linear2alaw(linear);
	 * System.out.print("  pcma:"+pcma); linear=ulaw2linear(pcmu);
	 * System.out.print("  linear:"+linear); pcmu=linear2ulaw(linear);
	 * System.out.print("  pcmu:"+pcmu); System.out.println(" ."); if (i%20==19) try
	 * { System.in.read(); } catch (Exception e) {} } }
	 */
}
